Ok, so the xenforo user is starting up a new process every 15 minutes without closing them, soon eating up all the server CPU. It looks like this:
MariaDB [(none)]> show processlist;
+---------+-----------+-----------+-----------+---------+-------+--------------+------------------------------------------------------------------------------------------------------+----------+
| Id | User | Host | db | Command | Time | State | Info...
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MariaDB [(none)]> show processlist;
+---------+-----------+-----------+-----------+---------+-------+--------------+------------------------------------------------------------------------------------------------------+----------+
| Id | User | Host | db | Command | Time | State | Info...
Read more
Continue reading...